Abstract
A new temperature-dependent cyclic plastic model, combining the nonlinear cyclic softening and kinematic hardening rules is established for a nuclear material of SA508-3 steel. A modified isotropic hardening rule is proposed to capture the temperature-dependent cyclic softening, and a modified kinematic hardening rule is established to improve the prediction of the ratcheting behavior by introducing an exponential function related to the accumulated plastic strain. The stress is updated by the radial return mapping algorithm based on the backward Euler integration. A new expression of consistent tangent modulus for the equilibrium iteration is derived, and then the proposed model is implemented into the finite element software ABAQUS by using the user material subroutine (UMAT) to simulate the temperature-dependent ratcheting behaviors of SA508-3 steel. Finally, the ratcheting evolutions of notched bars at elevated temperature are obtained by uniaxial stress-controlled cyclic tests, and the nonuniform strain fields on the surface of plates with a center hole is measured by using the digital image correlation (DIC) technology. Comparisons between experimental and simulated results of a material point and structural examples show that the implemented model can provide reasonable predictions for ratcheting behaviors and nonuniform strain fields of structures at different temperatures for SA508-3 steel.
Highlights
Ratcheting is a progressively accumulated inelastic strain under cyclic stressing with a non-zero mean stress
It is noted that ratcheting behaviors of SA508-3 steel are investigated at different temperatures in this work; each temperature is fixed in the process of cyclic loading, and the temperature gradient T and thermal strain rate ε can be neglected in following derivations
A temperature-dependent cyclic plastic model for SA508-3 steel, considering the nonlinear cyclic softening and kinematic hardening rules,model is implemented into a commercial finite element i.e., A temperature-dependent cyclic plastic for SA508-3 steel, considering thecode, nonlinear cyclic softening and kinematic hardening rules, is implemented into a commercial finite element code
Summary
Ratcheting is a progressively accumulated inelastic strain under cyclic stressing with a non-zero mean stress. Many progresses have been made to implement cyclic plastic models into commercial finite element softwares, such as ANSYS, ABAQUS, and so on. Based on the Abdel Karim-Ohno kinematic hardening rule [16], a cyclic plastic model with a memory surface was implemented into the finite element code ANSYS by using the UMAT [17], which provided a good prediction of the additional hardening caused by the non-proportional loading path. Motivated by the above considerations, the present work aims to implement a temperature-dependent cyclic plastic model into finite element software ABAQUS by using the UMAT for SA508-3 steel. Finite element models of structures including a notched bar and a plate with a center hole are established, and simulations are carried out to verify the implementation of the present temperature-dependent cyclic plastic model
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